1. Field of the Invention
The present invention relates to a device that creates a translation error compensation amount and a rotation error compensation amount both depending on a rotation axis, based on a preset assembly error and a rotation axis position in order to compensate an assembly error in a multi-axis machining apparatus having at least two rotation axes.
Now, the translation error compensation amount and rotation error compensation amount depending on the rotation axis will be described.
In “JIS B6190-7 FIG. 1 b) Error motion of rotation axis” of Japanese Industrial Standard, errors depending on a C shaft are represented as:
“EXC: radial motion in an X direction”,
“EYC: radial motion in a Y direction”,
“EZC: axial motion”,
“EAC: tilting motion around an X shaft”,
“EBC: tilting motion around an Y shaft”, and
“ECC: angular positioning error”.
According to the present invention, of the errors depending on a C shaft, “EXC: radial motion in the X direction”, “EYC: radial motion in the Y direction”, and “EZC: axial motion” are referred to as translation errors (specifically, translation errors depending on the C shaft). “EAC: tilting motion around the X shaft”, “EBC: tilting motion around the Y shaft”, and “ECC: angular positioning error” are referred to as rotation errors (specifically, rotation errors depending on the C axis).
For another rotation axis, for example, an A axis, the following are present: “EXA: axial motion”, “EYA: radial motion in the Y direction”, “EZA: radial motion in a Z direction axial motion”, “EAA: angular positioning error”, “EBA: tilting motion around the Y shaft”, and “ECA: tilting motion around a Z shaft”.
Thus, the translation errors and the rotation errors varying depending on the positions of the rotation axes are hereinafter referred to as translation errors and rotation errors depending on the rotation axes, and compensation amounts by which those errors are compensated are hereinafter referred to as translation error compensation amounts and rotation error compensation amounts depending on the rotation axes.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 2004-272887 (JP 2004-272887 A) discloses a technique for compensating an assembly error in a rotation axis in a multi-axis machining apparatus having rotation axes. The technique uses many matrix operations using triangular functions. Thus, the technique can be partly carried out in practice, but a numerical controller that needs to perform high-speed control takes a long time for arithmetic operations, and the technique is thus difficult to carry out in practice. Moreover, the technique disadvantageously fails to take into account an assembly error in a table surface, that is, an error between a table surface centerline and a table rotation axis rotation centerline, more specifically, an error in which the table surface fails to be perpendicular to the table rotation axis (C axis described below) rotation centerline and in which the table surface centerline deviates from the table rotation axis (C axis) rotation centerline.
On the other hand, Japanese Patent Application Laid-open No. 2009-151756 (JP 2009-151756 A) discloses a technique for compensating an error based on a translation error compensation amount and a rotation error compensation amount both depending on rotation axes. The technique performs matrix operations but does not take such a long time as needed for the technique described in JP 2004-272887 A. Thus, the technique disclosed in JP 2009-151756 A allows a numerical controller to perform compensation in practice. However, to determine the compensation amount, the technique divides a two-dimensional coordinate system for two rotation axes into pieces like a grid, sets a translation error compensation amount and a rotation error compensation amount at each of the resultant grid points, and calculates a compensation amount for the position of the rotation axis based on compensation amounts for grid points enclosing the position of the rotation axis. That is, the technique is not a method for obtaining the compensation amount from the assembly error. Thus, when an attempt is made to compensate the assembly error by the technique disclosed in JP 2009-151756 A, the assembly error needs to be converted into a translation error compensation amount and a rotation error compensation amount both depending on the rotation axes and to set the translation error compensation amount and the rotation error compensation amount. However, JP 2009-151756 A fails to disclose such a conversion technique.
Furthermore, Journal of Technical Disclosure No. 2009-505137 discloses a technique for creating the compensation amount disclosed in JP 2009-151756 A from the assembly error in a multi-axis machining apparatus (table rotating multi-axis machining apparatus) having two rotation axes for rotation of a table which is disclosed in JP 2004-272887 A. The technique fails to take an assembly error in the table surface into account. Journal of Technical Disclosure No. 2009-505137 describes a technique for creating a compensation amount from an assembly error in a rotation axis in a table rotating 5-axis machining apparatus and further states that the technique can be applied to a head rotating 5-axis machining apparatus (see FIG. 10) in which a head rotates based on two rotation axes and a mixed 5-axis machining apparatus (see FIG. 14) in which both a head and a table rotate.
However, the inventors have found that it is insufficient to apply the technique disclosed in Journal of Technical Disclosure No. 2009-505137 directly to the tool head rotating 5-axis machining apparatus or the mixed 5-axis machining apparatus. The reason is as follows.
In terms of an error in a member installed on a rotor, the assembly error in the tool head rotating multi-axis machining apparatus corresponding to the assembly error in the table surface in the table rotating multi-axis machining apparatus is an assembly error in a spindle turning centerline, that is, an error in which the spindle turning centerline fails to be orthogonal to the rotational centerline of a tool head tilting axis (an A axis described below). JP 2004-272887 A takes the assembly error in the spindle turning centerline into account while Journal of Technical Disclosure No. 2009-505137 does not take into account the assembly error in the table surface in the table rotating multi-axis machining apparatus as described above. Thus, even when the technique disclosed in Journal of Technical Disclosure No. 2009-505137 is applied to the tool head rotating multi-axis machining apparatus disclosed in JP 2004-272887 A, the assembly error in the spindle turning centerline fails to be compensated. This also applies to the mixed multi-axis machining apparatus.